1. Field of the Invention
The present invention relates generally to mobile stations which communicate with cellular networks and wireless local area networks (WLAN), and more particularly to the communication of cellular network information from one or more cellular networks to a mobile station through a WLAN.
2. Description of the Related Art
Within the cellular industry there is an initiative to configure wireless local area networks (WLANs) to communicate with cellular telecommunications networks so that mobile stations may be able to access both cellular networks and WLANs which provide a higher bandwidth. Traditionally, since WLANs were designed to provide only wireless local networking, there have been no existing protocols to provide advertisements to identify what cellular networks are available to a mobile station. Such information would be useful to provide the mobile station with the ability to identify and switch between different cellular networks and/or cellular network technologies as desired.
There is a further initiative to configure WLANs to be able to communicate with one to many different 3rd Generation Partnership Project (3GPP) networks. Such configuration requires that a Universal Subscriber Identity Module (U-SIM) be utilized by the mobile station to identify the end user or subscriber. The U-SIM also contains information that identifies preferred and forbidden cellular networks for the mobile station, each stored as a Mobile Country Code (MCC) and Mobile Network Code (MNC) pair.
Over a wireless link, a WLAN typically broadcasts a textual string called a service set identifier (SSID) to uniquely identify the WLAN to wireless units. Today, most WLANs have been deployed by corporations and wireless Internet Service Providers (ISPs) who use their specific SSID for branding or for “smart client” applications. Thus, WLAN operators are typically reluctant to change their broadcast SSIDs, and it is difficult to broadcast MCC/MNC pairs to mobile stations through WLANs without some protocol modifications. Other cellular network information may be useful to wireless units for making network selection decisions as well.
The Internet Engineering Task Force (IETF) has defined an Extensible Authentication Protocol (EAP) in RFC-2284 for easy extensibility and maintenance of authentication processes. There has been a proposal to extend the EAP mechanism for it to provide Global System for Mobile communications (GSM) network information. Several different cellular protocols for networks and mobile stations exist, however, and techniques to handle the communication of all such information is needed.